1. Field of the Invention
This invention relates to oxidizer gels for detoxifying toxic chemical or biological agents on site in the field.
2. Description of Related Art
The possibility of accidental releases or terrorist attacks with chemical or biological weapons has received increased attention. Methods for containing and countering the release of chemical and biological warfare agents are important for public health and safety, as well as national security. If a release occurs, the chemical or biological agents must be immobilized and neutralized or detoxified. Various methods have been developed to chemically detoxify agents such as nerve gases, mustard gas, or microorganisms like Anthrax. These methods, however, are not completely effective on all chemical and biological agents, are highly corrosive so that collateral damage is considerable, or require considerable time for reaction.
U.S. Pat. No. 5,678,243 to Yang et al. discloses a process for detoxification of chemical warfare agent VX and its analogs by hydrolysis. The hydrolysis takes place in the storage container over a period of weeks.
U.S. Pat. No. 5,710, 358 to Yang et al. discloses a process for detoxification of chemical warfare agents phosphonothiolates by reacting with a compound containing HSO5- ion, such as potassium monopersulfate. The reaction products are then hydrolyzed.
U.S. Pat. No. 5,763,737 to Yang et al. discloses a method for reducing the toxicity of methylphosphonothioate ions with hydrogen peroxide and a strong inorganic acid. The reaction is run over a number of days.
A method to detoxify mustard gases is disclosed in U.S. Pat. No. 4,949,641 to Sayles, which involves an initial reaction with a metallic powder and a subsequent deflagration reaction, or thermal pyrolysis.
Other methods to deal with toxic chemical and biological agents involve encapsulation and removal from a site for disposal. U.S. Pat. No. 5,584,071 to Kalyon et al. is a disposal method for highly toxic chemicals in which the chemicals are first neutralized and then encapsulated in a polymeric material. The neutralized, encapsulated products are then transported to a disposal site, where they can be incinerated or buried in a landfill.
Methods of immobilizing microorganisms are disclosed in U.S. Pat. No. 4,4,50,233 to Mimura et al. (using a polymer gel), and in U.S. Pat. No. 4,859,377 to Shasha et al. (using a starch matrix). A method for encapsulating chemical biological agents in a polymer matrix is disclosed in U.S. Pat. No. 4,344,857 to Shasha et al.
These methods are not practical for detoxifying a toxic substance quickly on site in a field situation. A need exists for a substance that can be applied directly to a contaminated area to destroy or detoxify the chemical or biological agents, which can then be washed, swept, or vacuumed away. In addition, the substance must be capable of being effectively applied to any surface or item. The substance must be fluid enough to be quickly and easily applied to surfaces, while viscous enough to adhere to angled or contoured surfaces. Such rheological properties may be achieved by the use of thickening agents.
Thickeners must be chemically compatible with the detoxification agents, such as oxidizing agents, in the substance. Unfortunately, foams and other conventional thickeners, such as those used in paints (TiO2), tend to be incompatible with oxidizing agents and are oxidized along with the targeted biological and chemical agents. Thus, a need exists for a detoxification substance that can be used anywhere in the field under emergency situations that contains thickening agents that are compatible with the oxidizing agents in the substance used to destroy the biological and chemical agents. This invention addresses the above-mentioned problems and provides an oxidizing gel having strong oxidizers and thickening agents that are compatible with the oxidizers.
The present invention provides a gel composition having oxidizing agents that act on the chemical and biological agents and thickening or gelling agents that are compatible with the oxidizing agents. It is an object of the invention to provide a method for decontaminating an area or items exposed to toxic chemical and biological agents, such as nerve gases, mustard gas, or Anthrax. It is also an object of the invention to provide a detoxification composition having a viscosity that can be applied on any contaminated surface. The rheological properties (i.e., flow) of the composition are such that the gel can be conveniently applied (e.g., sprayed or spread) on the contaminated area on site in the field.
The present composition has thickening or gelling agents made of refractory oxides, such as silica (fumed or precipitated), alumina, or alumino silicate clays. The oxides are in the form of colloidal solids, which form a gel when mixed with a solvent. The solvent can be water or an organic solvent. The oxides are compatible with the oxidizing agents used to oxidize the biological and chemical agents. Suitable oxidizing agents include hydrogen peroxide, potassium permanganate, sodium hypochlorite, potassium peroxymonosulfate, ammonium persulfate, peroxydisulfate, ozone, and ammonium peroxymonosulfate. A solution of the oxidizing agent(s) is mixed with the colloidal solids to form a gel. The viscosity of the gel depends on the concentration of colloidal solids; typically the concentration of solids is in the range of about 3-20% by weight.
The thixotropic and anti-sag characteristics of the gel allow greater concentrations of the oxidizing agent to be in contact with the chemical or biological agents. More uniform coverage of the exposed surfaces is achieved because of the colloidal attraction between the gelling particles. The gel can be applied to floors, walls, ceilings, and other localized sites for detoxification of open or closed areas, or recovery of equipment exposed to the harmful agents. The gel can reach otherwise inaccessible or hidden areas, such as cracks and ductwork. The gel can be applied by simplex or air assisted sprayers, rollers, brushes, or other techniques. Sprayers can apply the gel quickly for emergency applications.
The chemical and biological agents are entrained in the weak gel structure and are destroyed or detoxified by oxidation. The xe2x80x9cspentxe2x80x9d gel, wet or dry, can be washed away with water or other solutions, or removed by vacuum. The carrier solvent in the gel will evaporate over time, leaving behind a residue that can be vacuumed or swept up. The residue may be analyzed and disposed of as hazardous waste as needed.
Other objects, features, and advantages of the present invention will become apparent from the following description and accompanying drawings.